The combination of tower defense and hack-n-slash works fairly well together, though the classes are completely unbalanced. Melee is by far the easiest.

A great combination of music, nice visuals, and a unique style of light strategy. Easy enough for casual players, with Bastion type difficulty settings.

The art is bright and fun, but the narrator really makes this game fantastic - narrating every move as you shoot and smash your way through the story.

Needs a faster fast forward, and has a few annoyances if you're trying to get Expert achievements - but the normal gameplay is fun and well designed.

This is a fun but easy Diablo style dungeon crawler. It features quick travel via portals and spells, as well as a pet to sell items while you continue killing. Additionally there is a shared chest to transfer valuable items between characters

Shadowgrounds [Steam store page]
A reasonably fun top-down shooter with a sci-fi storyline. The NPCs occasionally block your movement during combat - luckily they don't seem to take team damage. The flashlight also runs out of batteries slowly, which pulls you out of the game a bit.

Corporate Lifestyle Simulator [Steam store page]
This game was originally named and bundled as "Zombies." before being renamed and released on Steam.

I wasn't a big fan of the melee combat, but once you get shotguns and SMGs it makes killing the management a much more pleasant experience.

Age of Empires II HD [Steam store page]
One of my favorite RTS - though it does suffer from the rock/paper/scissors syndrome once you know the game well enough. Age of Empires II: Conquerors Edition was a great expansion to the original game, and it's bundled into this HD remaster.

The main benefits are that this runs nicely on high resolution - the original was locked at something like 1024x768, and this also has a few tweaks like allowing higher unit maximums - raised from 200 in the original to 500 in this remaster.

I'm normally not a huge fan of re-releasing old games, but this one was such a classic, and the small tweaks they made improve the experience without ruining the nostalgia.